A known, much used system for validating transactions is that of associating a secret and personal code with a user, which code he uses when he must for example access a place or validate transaction through an electronic payment terminal.
One drawback of this system lies in the fact that the secret code may be stolen from the user, thus enabling a fraudulent individual to usurp the user's identity and act in his place. Another drawback lies in the fact that the user must remember his code to validate a transaction.
There also exists systems for authenticating a user, including biometry, commonly used to identify and/or authenticate users on the basis of individual physical characteristics and enabling the validation of transactions to be made secure.
However, one drawback of these prior-art biometric authentication systems lies in the fact that they are slow when used to reference a large number of users (for example to control access to an underground railway system in a large urban conurbation or to authenticate a user of a bank card).
Indeed, the duration of the verification step during which the authentication decision proper is taken depends on the number of users referenced in the authentication system. The greater the number of users referenced, the greater the number of potential comparisons that must be made to determine or not determine the authentication of a user.
There is therefore a need for a technique to overcome these drawbacks of prior-art transaction validation systems.